"Exhaustion" is defined here as the time when the pool of available addresses
in each RIR reaches the threshold of no more general use allocations of IPv4 addresses.
As ARIN have already reserved a /10 for the transition to Ipv6 policy, the low point
for ARIN is a completely depleted general use pool. For AFRINIC and LACNIC it the
threshold is a total of a /11 remaining in their available address pool.
This calculation also takes into account the redistribution of the IANA Global
Address pool, and in the simulation of exhaustion these addresses are redistributed
to the RIRs according to the policy.

The IPv4 address space is a 32 bit field. There are 4,294,967,296
unique values, considered in this context as a sequence of 256
"/8s", where each "/8" corresponds to 16,777,216
unique address values.

As noted in RFC 5735 a
number of address blocks are 'reserved.' There are a total of the
equivalent of 35.078 /8 address blocks that are 'reserved'. (This is
composed of 16 /8 blocks reserved for use in multicast scenarios, 16
/8 blocks reserved for some unspecified future use, a /8 (0.0.0.0/8)
for local identification, a /8 for loopback (127.0.0.0/8), and a /8
reserved for private use (10.0.0.0/8). Smaller address blocks are
also reserved for other special uses.)

The remaining 220.922 /8 address blocks are available for use in the
public IPv4 Internet. The current status of the total IPv4 address
space is indicated in Figure 1.

Figure 1 - Address Pool Status

This allocated number pool is managed by the Regional Internet
Registries, (RIRs) and the breakdown of IANA allocated address
blocks to each of the RIRs is shown in Figure 2.

Figure 2 - Address allocations to RIRs

Any individual IPv4 address can be in any one of five states:

reserved for special use, or

part of the IANA unallocated
address pool,

part of the unassigned pool held by an RIR,

assigned to an end user entity but not advertised in the routing
system, or

assigned and advertised in BGP.

The current
totals of IP addresses according to this set of states is shown in
Figure 3.

Figure 3 - Address Pools by State

This status can be further categorized per RIR, as shown in Figure 4.

Figure 4 - Address Pools by RIR by State

Another view of the address state pools is by grouping the address
space into a sequence of /8s, and looking at state sub totals within
each /8 address block. The following view shows the current status
of the IPv4 address space as 256 /8 columns each describing a pool
of 16,777,216 addresses.

Allocations

IPv4 Address are drawn from the Unallocated Address Number Pool,
administered by the IANA. These allocations are made to the
Regional Internet Registries (RIRs), and the allocation unit is in
units of /8s.

Figure 6 - Cumulative IANA Address allocations

This series can be further broken down by RIR.

Figure 7 - Cumulative IANA Address block allocations per RIR

Assignments

RIRs perform assignments of address blocks to ISPs and local
Internet registries. The cumulative number of assigned addresses
over time is shown in Figure 8.

Figure 8 - Cumulative RIR Address assignments

This data can be further categorized by RIR.

Figure 9 - Cumulative RIR address assignments, per RIR

RIR Pools

Each RIR allocates from its locally administered number pool. When
the pool reaches a low threshold size a further address block is
allocated by IANA to the RIR. The allocation quantity is based on
the allocation activity recorded by the RIR for the 18 months prior
to the allocation request, rounded to the next largest /8 address
block. The pool size within each RIR over time can be derived from the
allocation and assignment series data, producing the following
graph. This is indicated in Figure 10.

Figure 10 - RIR Address Pool size

The more recent data from this series is shown in Figure 10a.

Figure 10a - RIR Address Pool size

Advertisements

The next data set is total span of address space advertised in the
BGP routing table over time. The data has been collected
since late 1999. This is shown in Figure 11.

Models for Data Series

The foloowing figure constructs a relatively complete view of the
sequences of various address pools over time. Figure 16 shows the total amount
of space allocated by the IANA to the RIRs, the total amount of
space that has been allocated by the RIRs, the total amount of space
advertised in the routing table, the total amount of unadvertised
space that has been allocated, and the total amount of address space
that is held in the RIR's local allocation pools. This is indicated
in Figure 16. The objective here is to generate a predictive model
that can be used to extend these series forward in time in order to
estimate a point of exhaustion of the unallocated address pool

Figure 16 - IPv4 Address Pool Status

The more recent section of these series is indicated in Figure 17.
The approach used here is to take a recent sequence of data as the
baseline for a predictive model.

Figure 17 - IPv4 Address Pool Status - since 2000

IANA Data Series

Before looking in detail at the advertised address space, the IANA
allocation data and RIR allocation data will be examined, and a
relatively straightforward form of data analysis will be performed
over the data series.

The IANA allocation data is indicated in Figure 18.

Figure 18 - IANA Allocation Series

RIR Allocations

The RIR allocation data is indicated in Figure 19. This data is
shown in both its original format, and in a smoothed format, using a
sliding window smoothing algorithm, in a double pass of the
smoothing algorithm across the data.

Figure 19 - RIR Allocation Series

BGP Advertised Address Range

Modelling RIR Allocations

The approach used here to modelling overall address consumption levels is
to use the RIR allocation information as the baseline of the address
consumption model. This approach treats an address as "consumed"
once it has been allocated or assigned by an RIR. The data used to
construct the time series of allocations is the allocation "stats
file" published on a daily basis by each RIR, placed into a time
series, as indicated in Figure 9. The first order differential of
the smoothed total allocation rate can be generated, as shown in
Figure 27. A least squares linear best fit can be generated for the
recent part of this data.

Figure 27 - Rate of RIR Allocations - First order differential of allocation data series